A radio access method and a radio network for cellular mobile communication (hereinafter referred to as “Long Term Evolution (LTE)”, or “Evolved Universal Terrestrial Radio Access (EUTRA)”) have been considered in the 3rd Generation Partnership Project (3GPP). In LTE, an Orthogonal Frequency Division Multiplexing (OFDM) scheme is used as a downlink communication scheme. In LTE, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) scheme is used as an uplink communication scheme. In LTE, a base station is referred to as an evolved NodeB (eNodeB) and a mobile station (a terminal) is referred to as a User Equipment (UE). LTE is a cellular communication system in which the area covered by a base station is arranged in a cellular pattern into multiple cells, each served by a base station. A single base station may manage multiple cells. A single mobile station performs communication in single or multiple cells. The cell is also referred to as a serving cell.
In LTE, a Hybrid Automatic Repeat request (HARQ) to uplink data is supported. In a case where decoding of a transport block received on a Physical Downlink Shared Channel (PDSCH) succeeds, the mobile station in LTE transmits a positive acknowledgement (acknowledgement) (ACK) to the transport block on a PUCCH. Furthermore, in a case where the decoding of the transport block received on the PDSCH fails, the mobile station in LTE transmits a negative acknowledgement (NACK) to the transport block on the Physical Uplink Control Channel (PUCCH).
The base station in LTE performs scheduling of the transport block based on the ACK or the NACK received on the PUCCH. For example, in a case where the NACK is received, the base station in LTE retransmits the transport block. The ACK and the NACK are collectively referred to as a HARQ-ACK.
Furthermore, the base station in LTE transmits downlink control information that is used in the scheduling of the PDSCH, on a Physical Downlink Control Channel (PDCCH).
The mobile station in LTE determines a PUCCH resource that is used in the transmission of the HARQ-ACK based on a PDCCH resource with which the downlink control information is detected. Accordingly, the base station in LTE can dynamically change allocation of the PUCCH resource by adjusting the PDCCH resource that is used in the transmission of the downlink control information. Furthermore, the base station in LTE can cause multiple mobile stations not to transmit the HARQ-ACK on the same PUCCH resource (NPL 1 and NPL 2).
In the 3GPP, it has been considered to introduce an enhanced Physical Downlink Control Channel (ePDCCH) in order to increase the number of mobile stations that are accommodated in a cell (NPL 3). An ePDCCH resource is different from the PDCCH resource in the related art. To be more precise, the introduction of the ePDCCH extends the resource that can be used in the transmission of the downlink control information.
Furthermore, in the 3GPP, it has been considered to introduce Coordinated Multi-Point transmission and reception (CoMP) by which the mobile station can efficiently communicate with multiple base stations (NPL 4). For example, a certain base station may receive the HARQ-ACK to the transport block that is received by the mobile station from a different base station.